The present invention generally relates to composite materials having a high density of small particles such as microspheres in a matrix material and, more particularly, to various methods of manufacturing shaped articles from this material.
U.S. patent application Ser. No. 09/634,522, filed Aug. 8, 2000 (the xe2x80x9cCM applicationxe2x80x9d) discloses certain new composite materials. Such materials include a matrix material that has a high density of small particles such as, for example, microspheres disposed therein. The CM application teaches that there are a large amount of the small particles relative to the amount of the matrix material such that there is a high-density packing of small particles into the matrix material. An aspect of the invention disclosed in the CM application is that the small particles are positioned very close together, and many of the small particles may even be in contact with adjacent small particles. The CM application states that the matrix material fills the interstitial space between the small particles, and that the composite material can include a greater amount of small particles than matrix material by volume, weight and ratios or percentages of weight and volume. The content of the CM application is incorporated by reference into this application as if fully set forth herein.
The CM application states that a mixing and molding process was used to make sample composite material plaques that have a flat, generally square or rectangular shape. The CM application also states that microspheres were mixed with automotive grade polyester, phenolic or vinyl ester resins to saturate the resin with microspheres to form a core of clay-like uncured composite material mixture.
The CM application states that the clay-like composite material mixture core was flattened in a sheet molding compound (SMC) hydraulic plaque press into a flat, plate-like plaque shape, and then the flattened core was removed from the press. The CM application states that dry cross-woven carbon fiber was applied to both side faces of the composite material core. The CM application states that, optionally, filter paper (coffee-type filter paper) was flanked on both sides of the fiber/core/fiber sandwich-type structure and sealed on all four edges to form a sealed filter bag encasing the fiber/core/fiber structure. The CM application states that the encased structure was inserted into the hydraulic press, the press was heated, and the plaque press compressed the encased structure for approximately 3 minutes.
The heat applied during compression cured the thermoset resin, as stated in the CM application. Upon opening the press, the sample composite plaque was observed to have fully wetted-out the flanking woven fiber, and evidence of the microspheres was clearly visible through the transparent filter paper, as stated in the CM application. The CM application states that sample composite material plaques were pressed and cured in about 2xc2xd to 3 minutes, and that this is a remarkably fast manufacturing time as compared to slow curing resin molding which can require 8-24 hours to cure and an additional 2-6 hours to post-cure. The CM application also states that the ability to quickly manufacture products with the composite material disclosed therein provides significant advantages, such as high-speed manufacturing, continuous sheet production lines, and reduced manufacturing costs.
The CM application also teaches a sheeting process to make composite material boards. The CM application states that this process comprises a number of steps including, among others, the use of a pan, similar to a cooking sheet, for holding the components used to make the board, or other mold form having a desired shape. For example, the CM application states that woven fabric such as carbon fiber can be placed in the pan, a composite material can be placed on top of the carbon fiber, and that a second sheet of carbon fiber can be placed on top of the composite material.
The composite material disclosed in the CM application exhibits remarkable properties, and is suitable for use in a myriad of applications as discussed in the CM application. However, the manufacturing processes disclosed in the CM application are not operative to produce large numbers of articles in a continuous manufacturing process or producing molds for product development.
It is desirable to provide a method of manufacturing shaped articles utilizing a composite material having a high density of small particles such as microspheres in a matrix material that is capable of commercial scale applications. In accordance with one aspect of the present invention, a modified form of the composite material can be made using B-staged thickener to make a composite material having a high density of small particles in a matrix material that is thick enough to be handled manually. B staging chemistry is used to pre-consolidate the reinforcing materials (such as woven fabrics) to the composite material along a sheet molding compound line. In one embodiment, the composite material is formed into a desired shape or product using a compression molding technique.
Providing such a method has a number of distinct advantages. First, the process disclosed herein is suitable for a myriad of commercial scale applications in which large numbers of composite material articles may be formed and manufactured. Second, the process disclosed herein significantly reduces the material and labor costs associated with producing shaped composite material having a high density of small particles in a matrix material and manufacturing shaped articles therefrom. Third, this process allows for a more efficient creation of durable, strong, lighter weight products that have various commercial uses. The composite material forms a lightweight product that is easy to manipulate and use that has the additional advantage of being strong. These products can be used as a substitute for various metals (such as steel), and provide the necessary strength without the additional weight.
Other features and advantages of the invention will become apparent from the description that follows.